Aircraft having rotating blades or wings



R. H. PREWITT 2,509,367

AIRCRAFT HAVING ROTATING BLADES 0R wmas Original Fil'ed Dec. 18, 1940 3 sheetsus J 2 Figure 4 Figme INVENTOR, H. Prewii'i' ATTORNEY W WW R. H. PREWITT 2,509,357

AIRCRAFT HAVING ROTATING BLADES OR WINGS Original Filed Dec. 18, 1940 3 Sheets-Sheet 3 Figure IO "3 Fiqum '1 a 2 04 52 121,422

I g 105 8 s2 Patented May 30, 1950 2,509,367 AIRCRAFT HA ING ROTATING BLADES on WINGS Richard H. Prewitt, Wallingford, Pa., assignor to Kellett Aircraft Corporation, a corporation of Delaware originalapplie'ation December 18, 1940, Serial No.

370,572. Divided and this application November 3, 1944, Serial No. 561,695

Claims.

The present invention relates to rotary wing aircraft and more particularly to improvements in the drive, control and mounting of the rotative wings or blades of rotor systems and propellers.

This invention is further concerned with improvements in the mounting details of the wings and blades and with improvements in their construction for the purposes of reducing weight and friction. It also relates to improvements in the control and drive mechanism of the tractive and lift systems as well as to automatic interconnections between the blade pitch and drive mechanism controls of these systems in rotative wing aircraft. The present application is a division of my co-pending application Serial No. 370,572, filed December 18, 1940, relating to Aircraft having rotative blades or wings, which issued December 19, 1944, as Patent No. 2,365,357.

One of the major objects of the present invention is the provision of means for controlling the incidence angles of rotating blades of either horizontal or vertical thrust propellers, or of theretating wing systems of aircraft. A further object is the provision of such blades or wings which are operated under conditions of centrifugal tension without involving excessive friction; and to further improve such devices by the simplification and elimination of parts heretofore found necessary and to thereby provide structures which are lighter in weight. It is a further object of this invention to provide both manual and automatic means for controlling the pitch angle of rotor bladesand/or propellers while they are in operation in rotative wing aircraft of the jump take-oil type. Another object of the present invention resides in the provision of the improved mechanism for the starting of rotative wing systems and the transfer of driving power to the tractor propeller and the lift rotor. It is a further object to .provide a novel cable control arrangement for the actuation of the blade pitch-changingmechanism as well as an interconnection between the pitch change control system and the jump take-oif clutch control whereby the latter is automatically tripped when the blade pitch is manually adjusted into the high lift position. Other objects and advantages of the present invention may occur to those skilled in the art after a reading of the following description and the accompanying drawings forming a part hereof, in which:

Fig. 1 shows an elevation of an aircraft of the rotating wing type incorporating a tractor propeller and rotor system with a portion of the fuselage broken away to show the blade pitch control mechanism;

(c1. ire-135.73)

Fig. 2 is a detail drawing showing 'the operating lever for manual and/or automatic control of the blade pitch angles;

Fig. 3 shows a detail of the automatic clutch releasing device;

Fig. 4 shows an installation of the propeller blade pitch angle control device applied to a three-bladed tractor propeller;

Fig. 5 shows the application of the device to a two-bladed controllable pitch propeller;

Fig. 6 shows an elevation and partial sectional view of the hub and blade mounting assembly illustrating the method of varying the pitch angle of the blade;

Fig. '7 is a plan View of the mechanism at the hub end of the rotor blade as used for controlling its pitch angle;

Fig. 8 is a sectional view through the pitch angle controlling mechanism taken along the lines 8-8 of Figs. 6 and 7;

Figs. 9 and 10 show views of an end of the tension-torsion rods shown in Fig. 6; and

Fig. 11 is a detail view of one of the retractable blade stops.

Referring to Fig. 1, there is shown an elevational view of an aircraft of the rotating wing type provided for jump take-off, in which the general arrangement of the present invention is outlined. The aircraft I0 is comprised of the rotor system l,'composed in the present instance, of three rotatable blades mounted upon the hub 2 and supported from the fuselage of the aircraft by the .pylon 3. The rotor system I is arranged to be selectively driven through the universal joints 4 andthedrive shaft 5 by the rotor starter 6, and the engine 8, having an engine starter I, the engine also being arranged for the drive of the tractor propeller 9. The aircraft isotherwise provided with the usual landin gear II and tail surfaces [2 conventionally found on this type aircraft.

The tractor propeller is of the controllable pitch type, the blade pitch being controlled through the lugs l3 mounted on each blade and pivotally connected to the links I 4, the radially extending arms l5 journalled on bearing l6, and the slidable collar ll, all as more clearly shown in Fig. 5. The collar I! is pivotally connected to a link 18 and the bellcrank i9 pivotally mounted upon the engine at 19a and having its opposite terminal pivotally connected to the control rod 20 guided by the bearings 29b and terminating with a control handle 29a in the cockpit of the airplane accessible to the pilot. The clutch 21 which has been indicated in the drawing is of the external band type, but may be of any othersuittake-off with the rotor clutch engaged.

able construction, and is controlled through suitable arms 2|a, the push pull tubes 41, which are pivotally interconnected to the bellcranks 2 lb pivoted at 2|c and terminating in the arm 22, and the manually operated handle 23 which will be subsequently described more fully.

Referring now to Fig. 2, there is shown the conical in shape and that an internal portion 46a of the fork lips on lever 22 is sloped. The purpose of this arrangement is to permit conical stop 45 to move upward and to the right through fork arm 45 of lever 22 without creating any appreciable force on the end of lever 22. However,

' when stop 45 is moved downward in the opposite arrangement of the handle lever 24 and cable 25 1 a torque shaft 40 to levers 26 and 2'! and suitably journalled and supported by brackets 35a and 3522 from the fittings ma on the aircraft structure, being so arranged that when the lever 24 is pulled back against the stop 23 the slidable plunger 29 is moved forward so that its large circular section at 3|] substantially fills the hole in the tongue 3|a. in the plunger 3|. also be noted that when the lever is in the forward position the opposed stop 32 causes the plunger 29 to move back so that the small diameter of the plunger shown at 33 permits the plunger 3| to move up so that its upper face 35 comes against the lower edge of the quadrant 35 as shown in dotted lines in Fig. 2. The spring 3 lb in the upper end of the control tubular handle 24 will tend to keep the plunger 34 against the quadrant 35 when the control lever 24 moves up and back due to the force of the spring 31 (Fig. 1) acting on lever 21 through cable 4| which runs over pulleys 42, in combination with automatic control means rotating in the rotor head. As the control lever 24 moves back along the quadrant 35 the spring 3lb will force the upper edge 34 of the plunger 3| into notch 38 which represents the pitch angles of the rotor blades l in normal flight. Hand button 43 fixed to the plunger rod 3| provides a means of releasing the lever It should direction it will engage the fork end 45 of lever 22 as described.

Referring to Fig. 4, the nose of the engine is shown at 3 with the propeller shaft at 48 carrying either two or three radially extending stub arms 49 (Fig. 4 indicates a three-bladed propeller and a two-bladed system is shown in Fig. 5). The radial stub arms 49 are machined cylindrically at 5|} upon which are mounted bearings 5| at either end of the shaft stub. A circle of lugs 52 surround the radial arms 48 in a manner shown at the opposite blade at the bottom of the figure. The shank of the propeller is provided with the same type lugs also indicated at 52 and illustrated in greater detail in Figs. 9 and 10. In addition, the shank of the propeller 9 carries a machined shaft 53 which fits over bearings 5| located on shaft 50. Tension-torsion rods or links 54 are concentrically arranged about the center shaft in the same manner as shown in Fig. 8 for the rotor and are hooked over the lug projections 52 in the manner shown in Figs. 9 and 10. The control arm I4 is pivotally connected to the far side .of the shank of the propeller blade 9 through a pivot to and a control post I3 which is rigidly fixed to the shank of the propeller blade at a point outboard of the fittings 52. When push rod I8 is moved coaxially with the propeller shaft it causes collar I! to slide in and out along the propeller shaft 24 from its latched position in which the tongue 3|a engages the notch. When the lever is back against the stop 23 the blades are in low pitch and when it is down against the stop 32 the blades are in high pitch. When the lever 24 is pulled further aft than shown the terminal 39 of lever 26, continues to move downward about the pivot of the levers 24, 26 and 27 thereby pulling the rear terminal of cable 25 downwardly and rearwardly in relation to the pivot 48. The lever 28 is slotted in its upper section at 26a and pivot shaft 4c is recessed at 48a. directly'under cable 25, such that when the terminal point 39 is lowered sufiiciently so that the line of cable 25 :passes below the pivot At, or beyond the deadcenter, the tension in cable 25 due to forces acting on the rotor hub-end of said cable in combi both levers being displaced laterally as indicated by cable 4| passing lever 23 on the near side of the reader, therefore, levers 22 and 23 move together about pivot 44 transmitting the engaging load to push-pull rod 41. The lower end of 22 is formed into two open end lips straddling the cable 4| on which there is located a fixed stop 45. The purpose of the stop is to automatically disengage the rotor clutch 2| when the pitch control lever 24 is moved from low pitch to high pitch thereby preventing the possibility of a jump be noted that the fixed stop 45 on cable 4| is It will 48. This motion is transm ted through a hearing (not shown in this figure but illustrated at It in Fig. 5) to lever l5 which in turn causes the links l4 to move fore and aft substantially coaxially with the propeller shaft. This motion causes rotation of. the propeller blade 9 about the hub shank 49 and shaft portion 50.

The two-bladed propeller arrangement illustrated in Fig. 5 utilizes a slightlydifferent construction than the three-bladed system shown in'Fig. 4. It will be noted that the arrangement shown in Fig. 4 is equally applicable to propellers having any number of blades. In Fig. 5 the engine nose section is also shown at 8. The elongated propeller shaft 48 carries a fork yoke member 55 in which are mounted the shanks of the propeller blades 3 at 55 using any suitable bearing between yoke 55 and propeller blade 9, as for example, a bronze bearing, illustrated at 51. It will be noted that the machined shaft portions of the propeller shank ends shown at 58 andi59 are mutually journalled within the bearings. 5| which are located at the ends of the over-lapped or telescoped shank ends, thus providingadequate rigidity to assist in taking the bending moments of the propeller blades. The arrangement of the plurality of lugs 52 and the corresponding rods 54. are similar to those shown in Fig. 4 and in detail in Figs. 8, 9 and 10. Thus it will be seenthat the blades 9 are free to rotate in the bearings 5'! at shank position 56 and that when the blades are rotated inopposite directions the machined shank shaft 58 rotates in relation to machined shank shaft 59 on the interposed bearings 5|. The lugs and shaft portions are housed in a suitable fairing 122 for protection'and reduction in drag. r

It will be further seen that when the blades 9 pitch angle. Fig. is also similar to'the mechanism shown in Fig. 4;. For instance, the control posts I'3'are fixed to the propeller blades 9 near their shanks and the pivots 60 onthe corresponding sides ofthe shankssuch that fore and aft motion of the connecting link I5 causes theblades 9to turn in their" respective pivots 56; The motion of the control link M is controlled through the pushpull members l8 and 20, through the lever l9 pivoted at Illa, collar I1, bearing I6 and control arms I5, in a manner as described above.

Fig. 6 shows an assembly elevation of a cutaway section of the rotor hub 2, the extension link 6!, rotor blade fork 62, and the blade pitch change operating mechanism, a clarification of this figure being shown also in the plan view of Fig. '7. Hub case 2 carries a cap arm 63 attached to its upper end in which are mounted radial bearing 64 and thrust bearing 65'. At the lower end of hub case 2 is an inserted end plate 66 which carries bearing 61 and fixed sheath portion 69 of the Bowden cable 25. The hub shaft 69 rotates in bearings 64, 65, and 51; The bearings E i and 65 are clamped in place through collar it which is threaded on to the rotatable hub shaft I59, the main lift loads being taken through this collar into hub cap 63. The beveled gear I! is splined to hub shaft 69, and clamping nut 12, which is threaded to shaft 69, maintains gear H and bearing 61 in fixed position relative to shaft 69. Within the hollow part of the hub shaft 69 is mounted a stand pipe 82 which is fixed to and sealed with hub end plate 56 and 66a at its lower end. The hub end of cable 25 is fixed in swaged end I5 which is in turn screwed into member I4. Member Hi carries a projecting lug at I3 which moves in a parallel slot 82a in stand pipe 82, thus the assembly of members I4 and I5 and cable 25 are fixed so that they cannot rotate in relation to the hub case 2. Between member !4 and rod 19, bearing 16 is inserted. Nut 8| at the lower end of rod 19 anchors the latter to the inner portion of bearing 16. Just above bearing 16 rod 19 is expanded into a disc 83 to which are attached swaged ends 18 at the end of cables 84, only one of which is shown. In order to cause rod I9 to rotate with hub shaft 69, rod I9 is triangularly shaped in cross section. Guide plate 80 which rotates with hub shaft 59 likewise has a triangularly shaped opening to fit rod 79. By this mating of the two irregular parts, that is section of rod 19 and plate at, the assembly above bearing 56 rotates with the hub shaft 69. In modifications where it might be desirable to assist the cable 25 in drawing the assembly downwardly within the stand pipe 82 to maintain the desired tension in cable 8d, a tension spring is preferably attached between the member M and the bottom plate 65, or 66a.

Extension links 6 I are attached to hub shaft 69 through pivot 85 carrying a droop stop 86 and coning stop 81. On the top of hub shaft 69 are mounted brackets 88, supporting pulley housing 6. 89 whicli isl rockable about pivot: 90. pulley- 9I-2 being I mounted within the rockablepulley bracket 89". M Therockable position or pulley housing 89. is determined by the conedzposition of I the blade through'the action of the roller 92- and flat sur-. face 93 which moves with theblade. The plate- 93; attachedto extcnsionarmtl through clamp structure 94 will causepulley guard 39 to rotate about'pivot Bil-carrying pulley 91 alongw-ith the guardthereby changing the length of cable 84 to compensate for the normal decrease inthe length of thiscable' which would occur if this compensating device were not incorporated. Pulleys 95 and. 96 are also fixedly attached to clamp9 i leading. cablefl'd out to the blade incidence angle control mechanism without being. substantially affected changes in the coning angle of the blade. Blade fork arm 62 is attached to extension link BI throughverticalhinge 97. A suitable internal self-centering damper is provided, operating on centering cam 98 and limited in its motion by the disappearing stop 99, having its inner telescoping part bearing against lug 61a and the interposed spring 99a as shown in detail in Fig. 1.1. The tapered pin 99' engaging the portion 62a. of the fork arm limits the movement of the latter but when it is desired to fold the blades together the pin is" merely pushed in against the spring and rotating the same a quarter turn with a screwdriver, whereby it is locked in its retracted position.

A self-aligning bearing It!!! is fitted over the outboard stub end 62a of the fork 52 and within the blade shank IOI. The lugs 52 and tensiontorsion rods 54- are similar to those described previously, as shown in Figs. 4 and 5', and to be subsequently described in connection with Figures 8, 9 and 10, and they carry the centrifugal loads between the blade member I01 and the blade fork 62. In fiight the rubbing faces I02 between members 62 and HM, are held apart due to the centrifugal load in the blade I. In this condition of operation, bearing I00 transmits only the shear load resulting from whatever bending there may be in members 62 and ItI. When the machine is at rest with the blades drooped in cantilever fashion the upper tension-torsion members 54 transmit the tension part of the bending load introduced by the cantilever blade, and the compression part of this load is transmitted by a contact between the faces Hi2 between fork B2 and blade shank IOI. In practice it has been found desirable to incorporate shims at these surfaces for the purpose of adjustment and control or wear. It may be seen that the blade will be held in cantilever position when stop 86 on extension link 6| droops or rotates downwardly against mating section hub 59.

A better visualization of the arrangements and operation of spring I03 and controlling levers m8, I09 and I I0 can be obtained by a study of Figure '7 which is a plan view of the blade root section shown in Figure 6. The pitch control levers I08 and III] are pivoted at I05 and I05 to the fork B2 and the blade shank IOI, respectively, and in conjunction with the interconnecting link I 09 pivoted at I06 and I07, a parallelogram linkage is formed. Due to the relative angularity between the pivots I04 and I05 in combination with the parallelogram motion illustrated, blade shank member IOI may be angularly rotated relative to blade fork 62 when cable 84 is lengthened or shortened. From a study of Figs. 6 and 7 it may be seen that arm I08 is pivoted to the fork 62 at a'cocked or skewed angle. It will also be seen asoaser disc. A double pivot arrangement is provided at the 'outboard end of lever I08 where it connects to link I09. It will be seen that the pivot at I01 will also move vertically when lever I08 is rocked outboard or inboard. Since link I09 is connected to lever IIO through a self-aligning bearing at pivot I01 it will cause lever arm I I to move the blade shank IOI as a result of its forked pivot arrangement on blade shank IOI at pivot I05. The cable 84 is also pivotall connected to the pivot I01 by the clevis H8 and the turnbuckle H0. Lever I I I] is limited in its outward motion by stop II! which is adjusted for the highest pitch position of the blade. To the for-ward end of arm I I I is attached a lead weight I I2 which may b made up in parts as desired. This weight arm I I I is attached to lever IIO as though they were a single.

member so that when lever IIO moves outboard, weight II2 moves inboard. Weight arm III and its component weights II2 are used to obtain a proper balance in the system. The effective weight of the lever assembly I08, I09 and H0 withtheir bearings,'etc, is greater than the momentive effect of the weight arm II I and weights H2, therefore, when the centrifugal tension increases due to increased rotor speed, the assembly or arms I08, I09 and I I0 tends to move outboard toward the stop II! with increasing magnitude according to rotor speed squared.

On the'other hand, the spring I03 is swivelled about the pin I it which passes through pivot I05 at one end, and swivels about adjustable pivot H3 at the other end, the'tension in the spring being adjustable at H4. The springpivot H3 is supported by bracket II5 which is fixed to the fork 62. It will be seen that the spring I03 augmented by tension in cable 84 tends to pull the blade into low pitch position and the centrifugal force acting on the arms I08, I09 and III] tends to cause the blade to go into its high pitch position. In order to equalize the adjustment in the several blades that may comprise a rotorsystem, only oneof which is shown, the cable '84 is connected to the strap II B through the adjusting turn-buckle H9. Additional tension in cables '84, as mentioned above, is derived from the tension in cable 25 resulting from the action of th cockpit spring 31 on arms 26 and TI and attachment 39 of Fig. 2. K I

.In Figure 8 there shown a section taken through the tension-torsion rod assembly of Figure 7 at line 88 showing the tubular section of 1 fork 62 and the circumferentially arranged'ten- .sion-torsion rods 54. Figure 9 is an enlarged safety retaining wires I2l which keep the tensiontorsion rods 54 from moving off of lugs .52. The hardened insert part I20 is fitted into theirregularly'shaped slot 54a in rods 54. v This insert has a convex surface I20a where it rests againstlugs 52, thus when blade shank IIlI of Figured is rotated relative to the fork 52 the outboard ends of the tension-torsion rodsfare rotated .With the blade shank IOI while the inboard ends of these rodsrare held stationary since they are attached jforward or rearward motion of lever 24. enlarged portion 36 is in engagement with the to fork member 62. It may readily be seen that when this occurs the tension-torsion rods '54 are rotated or rocked on the lugs 52 and the convex surfaces of the hardened inserts I20 permit a rocking motion rather than a sliding motion thereby reducing the friction to a minimum. It may be noted that tension-torsion rods 54 are cut out with an outwardly tapering clearance in the opening 54a to permit the aforementioned rocking motion without binding against the lugs 52, and the entire assembly is housed in a fairing I22. There'are-two sources of forces which tend to keep a blade suspended in a given position. The first is the individual twist or torsion introduced in the tension-torsion rods 54 resulting from angular displacement of the blad about its longitudinal axis relative to the fork arm 62 in Figure 6, or shank 49 of Figure 4. This centering force is proportional to the angular displacement of the blade with respect to the hub to which it is linked. The second source of centering of the blade toward the neutral position is brought about when the tension-torsion rods 54 are skewed away from their normal position (parallel with the axis of the blade or blade shank) while centrifugal tension is acting on the blade. In this case the centrifugal forces tend to straighten out or keep the rods parallel to the center line of the blade shank. Any displacement from the parallel position requires that a torsional force be applied to the blade. This force will be proportional to the centrifugal force (R. P. M. squared) and the angular displacement of the blade from its neutral or normal attitude.

In the operation of the jump-take-off control mechanism the engine 8 is started in the usual manner by means of its starter I with the-rotor clutch 2| disengaged and-the handle 24 in its rearward or zero lift position; At the same time, in order that forward motion is not imparted to the craft by the tractor propeller 9, the blades of the latter are adjusted by means of the handle 20a into their low pitch position. The rotor system l is then started by its starter 6 and its continued rotation is transferred therefrom to the engine 8 by engagement of the clutch 2 I The clutch 2!. is engaged by rearward and upward movement of the manual handle 23 about the pivot 44 as shown in Figure 3. The resulting rearward movement of the secondary clutch lever 22 and its forked terminal 46 is unimpededby the stop 45 on the cable 4I inasmuch as the latter is also in its rearward position as determined by the rearward position of the blade pitch control lever- 24, the stop 45 having been drawn rearwardly by the tension spring 31.. The rearward movement of the stop 45 from a position forward of the lever terminal 45 is permitted due to the correspondingly sloped surfaces 46a and such movement of the stop rearwardly does not interfere either with the. released or engaged setting of the clutch lever. While'the engine is running in this manne with both the tractor and lift blade systems rotating, the pump takeeoff is initiated by pushing the lever 24 forwardly intothe high lift position of the rotor blades. At the same time the plunger rod IiI has been drawn downwardly due to the engagement of the enlarged circular section 3 0 of the slidable plunger 29, with the opening in the tongue tic such that it may pass freely past the notch 38 in the quadrant 35 on either the The "3 9. W l I 0 the end of the slidable' plunger 29 having engaged the stop 28 in the rearward zero lift position of the handle 24. Likewise, when the hand lever has been moved into its extreme forward or high pitch position the transversely slidable plunger 29 is pushed backwardly and rearwardly as a result of its engagement with the forward abutment or stop 32 in which position the reduced neck portion 33 of the plunger 29 releases the plunger rod 3! to the influence of the tension spring lllb, causing the edge 34 to bear against the lower edge of the quadrant 35. This forward movement of lever 24% causes the concurrent forward movement of the levers 26 and 2'! which releases the blade pitch increase tendencies due to slackening of the cable 25 and increased tension in the cable ll causing the stop t thereon to be moved forwardly into the dotted position shown in Figure 3. This for ward movement of the stop 55 engages the forked terminal to of the lever 22 causing automatic throw-out or release of the clutch 2 l, simultaneously with the increase in lift of the rotor system. The power developed by the engine now becomes available for forward thrust and when sufficient altitude has been obtained by the lift of the rotor system which rotates for an appreciable period due to the stored energy in the form of inertia, the pitch angle of the propeller blades 9 is increased by operation of the manual control film forward motion of the craft is obtained. The pitch of the rotor blades can then be manually restored to its normal setting by drawing the handle 2% rearwardly until. the tongue em engages in the notch 38 where it is latched or locked and the other necessary controls may then be adjusted for the continued flight of the craft. Since the moment-a1 weight of the arms let, Hi9, Hi3, iii, H2 and their assembly is greater on the rearward, or side where the arms are disposed, than on the front or leading side where the Weight H2 is located, increasing rotor speed causes said arms to exert an increasing effort to move outboard against the resistance of the spring Hi3, and. the forcein the cable 84%. On the other hand, as the rotor speed decreases, the force in the cable 34 due to spring 3? combined with the momental force in the spring 1533 about pivot Hi l, including centering effect of the tension-torsion rods, willbeconie greater than the unbalanced centrifugal force (as described above) acting on the assembly of control i733, ibii, I Hi, I i l, l 52. When-this occurs spring operating through cable 4i and arm forces lever backwards from the highpitch position. When lever 24 reaches the normal pitch position latch pawl 3 la. automatically engages notch in quadrant This automatic feature is brought about by the fact that the springs in the system tend to pull the unbalancedweight on the control arms of the blades inboard with a substantially constant force (at any given posi ion of the arms) the centrifugal force acting on the unbalof said control arms tends to pull 1 outboard substantially proportional "eed square. It may readily be seen an rotor speed the blade pitch would whereas at higher rotor speeds an inane tendency would be for pitch of the rotor blades to increase, and at lower than normal speedthe automatic tendency would be to lower the h angles of the blades.

e are two specific examples in which. this auton tic adjusting feature of the rotor blade depending upon the rotor speed be utilized: (a) In a designof a power driven rotor it may 10 be found desirable to have the rotor blades automatically increase their pitch angle with. increas ing speeds of the rotor, and conversely to automatically decrease their pitchangle with decreasin speed of the rotor. This can be readily accomplished with the present invention.

(7)) Where it is desired to use the kinetic energy of rotor turning at greater than normal speed for increasing the take-off performance of either the power driven or the autorotating type rotor, the system works as follows: With lever 24 in its rearmost position (blades at zero lift), the rotor blades are set in motion either through power from the engine 8 drive Shaft, etc., or through an external source of power. It maybe noted that the least power is required for turning the blades when they are at their angle of attack of minimum drag (substantially zero lift). In this attitude with a given source of power the blades may be turned to their greatest rotational velocity, which may be much greater than the normal speed of rotation in flight. The speed of rotation which is greater than normal represents stored kinetic energy which can be made available for increasing take-off performance of the machine, which is accomplished as follows:

The over center latch effect of cable 25 below pivot at when stop 29 engages stop 28 holds lever 24 in its rearmost position, as the speed of the rotor increases the unbalanced momentof the assembly of the control arms I08, I09, H0, Ill and H2 creates an increasing unbalanced centrifugal force acting on said arms which is car ried through cable 84 and units 18, [1; bearing to; case hi, and part 15 to cable 25. Thus when lever Ell is pushed forward to the extent that cable 25 passes above pivot 40, the increased force in cable 25 will immediately force lever 24 to its most forward position, shown in dash lines on Figure 2. If a limitation is desired to reduce the rapidity with which the pitch angles are in creased, a suitable dash pot or damper cylinder 2%, may be pivotally connected at 39 in Fig. 2 or may be inserted anywhere in the system at which it will retard the forward motion of cable 25.

When the blades are in their high pitch position the aerodynamic drag on the blades is iricreased and the tendency is to rapidly slow down the rotational speed of the rotor. When the speed of the rotor is slowed down, as mentioned above, the force of the springs acting on levers let, 5G9, H0 tends to pull them inboard and adjust the pitch to a lower angle of incidence, thus the system operates automatically.

It will be seen from the foregoing that suitable means have been provided for permitting angular adjustment of the blades of both the tractor propeller and rotating wing system, in relation to the axis of rotation of either without the development of appreciable friction while the centrifugal forces are acting upon the blades. This has been accomplished by transferring the centrifugal tension, in the case of the rotor system, from the blade llll to the fork arm 62 through the plurality of rods 54. Because of the convex surface lZEa on the insert [20, which fits in the slotted portion 540. of the ends of the rods 54, the motion between each rod'and its mating lug as shown in detail in Figs. 9 and 10, is a rocking motion rather than a sliding motion and therefore the only friction present is due torolling friction which is obviously extremely small. In addition the small bearing I00 mounted internally at the outboard connection of the rods 54 develops an extremely small amount of friction inasmuch as it transmits only the shear load from the blade llll to the forked arm 62. The self-centering effect which is obtained by this construction also causes relatively high torsional frequencies of the blade and thereby permits successful feather control installations. The foregoing features of my invention are relatively important in that a means has been found for permitting adjustment of the blade pitch while under centrifugal tension, but without introducing appreciable friction into the system; and also in that the construction shown for making blade incidence adjustments can be made much lighter than prior arrangements and methods which involve the use of thrust bearings and the like.

Other advantages and modifications of the present invention which may occur to one versed in the art, both in general arrangement and detail design, are all intended to fall within the scope and spirit of this invention, as set forth in the appended claims.

I claim:

1. A blade pitch control mechanism for a rotative wing aircraft comprising a quadrant fixedly supported upon the aircraft, a hand lever pivotally mounted for movement along said quadrant, said quadrant having portions corresponding to low, high'and intermediate normal pitch settings, abutments carried upon said quadrant disposed in the path of said hand lever adjacent the limits of its movement, a recess in said quadrant at said intermediate normal pitch setting, latch means carried by said lever engageable with said abutments, said latch means retracted upon contact with said low pitch abutment and extended upon contact with said high pitch abutment whereby said lever is latched in the recess at said'intermediate normal setting in movements from said high limit to low settings only.

2; In a rotative wing aircraft of the jump takeoff type, an engine, a rotor blade system, drive mechanism including a clutch associated with said engine for driving said rotor system, manual means for actuating said clutch and a rotor blade pitch control mechanism comprising a hand lever pivotally supported upon the aircraft for movement along a quadrant, a lever mounted for movement with said hand lever, adetent-carrying cable attached to the first of said levers adapted to engage said clutch control means for the disengagement of said clutch upon movement of said hand lever from its low to its high pitch position and a cable interconnecting the terminal of said second lever with said rotor blade system for its pitch adjustment, the angle of said second lever being disposed in relation to the run of said pitch adjusting cable such that the latter is deflected beyond a dead-center position and said manual lever thereby releasably retained in its low pitch position.

3. Rotor blade pitch change control mechanism as set forth in claim 2 characterized by the provision of damping means interposed between said aircraft support and said dual and hand lever elements for restricting the speed of said blade pitch changes. I

4. In a rotative wing aircraft having an engine carried by the aircraft, a rotor system having adjustable pitch blades rotatably mounted upon the aircraft, drive mechanism including a clutch associated with said engine for driving said rotor system, and manual means for controlling said clutch, pitch control mechanism for the adjustment of the blades of said rotor system comprising a hand lever pivotally supported upon the aircraft for adjusting movements with respect thereto, detent-carrying means attached to said hand lever arranged to automatically disengage said manual clutch control means upon movement of said hand lever from its low to its high pitch position, said hand lever having a normal pitch position intermediate said low and high blade pitch positions, and automatic latching means cooperatively associated with said hand lever for releasably latching said hand lever against movement at said normal position in moving from said high to said low pitch positions only.

5. A rotor blade pitch control mechanism for a rotative wing aircraft of the type set forth in claim 4 characterized by the inclusion of manual release means carried by said hand lever arranged for the selective release of said latching means at said normal pitch position and stop means disposed adjacent said low position arranged upon contact by said latching means to cause retraction of said manual release means to prevent its said automatic latching until said latching means makes a subsequent contact with fixed structure at said high pitch position.

6. In a rotative wing aircraft having a power plant, a tractor propeller driven thereby, a variable pitch lift rotor system, a clutch for the selective drive of said rotor system by said power plant, manual means for adjusting the pitch of said rotor system, and manual means for engaging said drive clutch, automatic means interconnecting said manual pitch adjusting means and said manual clutch engaging means comprising flexible means having a first terminal resiliently anchored to the aircraft and a second terminal attached to said manual pitch adjusting means, a tapered notch carried by said clutch engaging means, a detent carried by an intermediate portion of said flexible means, and means for guiding said flexible means through said tapered notch arranged in such manner that as said manual pitch adjusting means is moved into its increased pitch position said detent is caused to move in a direction in which it imparts releasing movement to said manual clutch engaging means and the resulting disengagement of said drive clutch for the automatic transfer of the available power of said power plant from said lift rotor system to said tractor propeller.

7. Automatic pitch and clutch control mechanism for a rotative wing aircraft having a power plant, a tractor propeller driven thereby, a variable pitch lift rotor system, a clutch for the selective drive of said rotor system by said power plant, manual means for adjusting the pitch of said rotor system, and manual means for engaging said drive clutch, said automatic pitch and clutch control mechanism including flexible means interconnecting said manual pitch adjusting means and said manual clutch engaging means, said flexible means having a first terminal resiliently anchored to the aircraft and a second terminal attached to said manual pitch adjusting means, a notch carried by said clutch engaging means, a detent carried by an intermediate portion of said flexible means, and means for guiding said flexible means through said notch arranged in such manner that as said manual pitchadjusting means is moved into its increased pitch position said detent is caused to move in a'direction in which it imparts releasing movement to said manual clutch engaging means with resulting disengagement of said drive clutch for the automatic transfer of available power of said power plant from said lift rotor system to said tractor propeller.

8. In rotative wing aircraft, rotor pitch control mechanism including a hand lever pivotally mounted for rotation upon fixed aircraft structure, a quadrant along which said hand lever is arranged to be moved, said quadrant having terminal abutments adjacent the low and high pitch positions of said hand lever, said quadrant provided with a detent at a normal pitch position intermediate said high and low positions, an element movably mounted upon said hand lever adapted to engage said quadrant terminal abutments, detent engaging means carried by said hand lever controlled by said relatively movable element arranged in such manner that said hand lever is adapted to pass freely through said detent in said normal pitch position when moving from the low to said high lift positions but is arranged to be latched within said detent in said normal pitch position upon return movement from said high pitch position toward said low pitch position.

9. In rotative wing aircraft, a rotor pitch control mechanism of the type set forth in claim 8 characterized by said movably mounted element being supported upon said hand lever for relative movement with respect thereto and within the rotative plane of movement of said hand lever, said relative movement initiating actuation of said detent engaging means when moved in one direction wtih respect to the hand lever and having no efiect upon said detent engaging means when moved in the opposite direction.

10. In rotative wing aircraft, a rotor pitch control mechanism of the type set forth in. claim 8 characterized by said movably mounted element having a camming portion, said detent engaging means having a portion engageable with the camming portion of said movably mounted element for initiation of the said control of the detent engaging means for the actuation of said detent engaging means to latch the hand lever wtihin said detent in said normal pitch position upon return movement from said high pitch position only.

RICHARD H. PREWIIT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,871,124 Landrum Aug. 9, 1932 1,987,650 Wiegand Jan. 15, 1935 2,074,342 Platt Mar. 23, 1937 2,076,090 Myers Apr. 6, 1937 2,080,540 Isaac May 18, 1937 2,183,119 Larsen Dec. 12, 1939 2,263,304 Larsen Nov. 18, 1941 2,324,588 Larsen July 20, 1943 2,365,357 Prewitt Dec. 19, 1944 2,375,465 Campbell May 8, 1945 2,393,158 Grace Jan. 15, 1946 2,421,364 Cierva May 27, 1947 FOREIGN PATENTS Number Country Date 844,908 France May 1, 1938 

